The penalty comes after Palou received an engine change between Carb Day and the 105th running of the Indianapolis 500 last month.
Palou confirmed the penalty in a pre-event press conference, which comes as a result of a new rule that was introduced in 2020.
The rule stipulates that teams cannot undergo an early engine change in the season, necessitating a six-place penalty on road and street courses and a nine-place penalty on ovals.
Rule 16.5.4 reads: “Once an Indianapolis 500 Engine is fitted to the Car, removal of the Engine prior to the Indianapolis 500 Race is an Unapproved Engine Change-Out, unless it is for Repair”.
If an engine change is made at the Indianapolis 500, the penalty can only be served in the following race.
Palou said he expects an uphill battle going into the weekend's first race at the Belle Isle Street Circuit at what will also be the first time he has raced at the street circuit.
Last year the series did not race in Detroit due to the COVID-19 pandemic.
“If I would have three free practices like they used to have before, I would be happier, I guess, learning a new track on a street course and still trying to get myself to the limit and then get the car to the limit – but it is what it is,” said Palou.
“It's going to be alright. I think it's going to be tough the first qualifying because, as Ryan [Hunter-Reay] said, it's so competitive.
“It's so close that when you are not at 100 percent and you are not 100 percent confident with the car, you lose one or two tenths and that can give you a P5 or a P15.
“We also have a grid penalty for the first race, so that's going to make our stuff really hard. We'll try and have some clean and good strategies, and we'll be up there by the end of the race.
“It's going to be challenging for sure,” he added.
“I've never been to Detroit. The track looks awesome. Looks really bumpy. But yeah, I think the layout, it's super nice as a street course.
“I think it's super good for me that there's a double race. I know I have a second chance on Sunday.
“Having the free practice on Friday, that's going to help me to slip in and rethink everything that I did for the first qualifying.
Palou heads to Detroit in the knowledge that Chip Ganassi Racing will be competitive.
Dixon has three wins at the circuit to his credit in 2012, 2018, and 2019.
“The team had really good results the past years, so I know that Scott is going to be fast,” said Palou.
“Marcus [Ericsson, team-mate] got his first podium there in '19, so he's going to be really quick, and yeah, I'll be able to learn from all of them and hopefully we can be up there.
“I'm sure it's going to be a great weekend.”
This weekend's Detroit Grand Prix at the Belle Isle Street Circuit will comprise two 70-lap races.
The opening race in the Dual in Detroit gets underway at 04:00 AEST on Sunday, June 13 with the second race at 02:00 AEST on Monday, June 14.